Residual amount of water in a draining curd of camembert cheese and physicochemical characteristics of the drained curd as modified by the pH at renneting, the casein concentration and the ionic strength of milk

Abstract

Camembert soft cheeses were prepared from cheese milk modified using membrane tech- nologies to obtain different casein contents (27-37 g.kg -1 ) and different ionic strengths estimated from the dilution factor of milk with a lactose solution (0.6 compared to 1.0 in normal milk). Renneting was performed at pH 6.0 or 6.4. The amount of water remaining in the draining curds, expressed as the water to casein ratio, R (g .g -1 ), was calculated from the whey drainage kinetics data. A kinetics of variation of R during drainage was obtained in each of the experimental conditions and was characterised by fitting with a descriptive mathematical model involving 2 relaxation processes and 5 parameters: R (g water.g -1 casein) = R1 exp(-t/τ1) + R2 exp(-t/τ2) + R3. The R values at the end of drainage, obtained from the model for t = 1 000 min, fitted well with the water amounts determined in the drained curds by chemical analysis. The values of the equation parameters, obtained by fitting the equa- tion to experimental data, were correlated to the levels of factors which were varied in the experiments. This allowed a mean value for each parameter to be obtained, and values for the effects of factors. The amount of water remaining in drained curd at the end of drainage was dependent on the milk casein content and pH at renneting factors through a negative effect. Prediction of final values of R by cal- culation from this data was possible. However, the correlation with experimental values was low. In addition, the drained curd composition and rheological properties were determined and the effects of the factors on these curd characteristics were quantified. A positive effect of the pH at renneting on the dry matter and ash contents of drained curd was observed. Incidentally, these factors also mod- ified its rheological properties.